FAQ
TL;DR: A 1.5 mm² wall-embedded copper cable carries only 14 A continuously [Elektroda, TWK, post #14611334]; “socket load is 16 A max” [Elektroda, ciuqu, post #14610408] Up-rating the breaker to 20 A overheats the wire and breaches PN-IEC 60364 rules. Why it matters: Oversized protection can start a fire long before the fuse trips.
Quick Facts
• Polish socket rating: 16 A / 3680 W max [Elektroda, Anonymous, post #14613277]
• 1.5 mm² cable current limit in wall: 14 – 15 A at 25 °C [Elektroda, TWK, post #14611334]
• 2.5 mm² cable limit (method C): ≈ 20 A continuous [PN-IEC 60364-5-523]
• Loads > 2 kW should get a dedicated circuit per N SEP E-002 [Elektroda, kkas12, post #14610595]
• Typical B16 breaker trips at 23 A within 1 h; B20 at 29 A [ABB, 2021]
Can I simply replace my B16 breaker with a B20 to run a 200 A MIG welder?
No. A B20 allows up to 29 A for an hour, well above the 14–16 A that 1.5 mm² wiring and a standard socket can survive, risking insulation damage and fire [Elektroda, rtvserwisant, post #14610380]
Why is 16 A the upper limit for Polish Schuko sockets?
The socket contacts, clamps and plastic housing are certified to 16 A continuous (3680 W at 230 V). Higher currents overheat the spring contacts, melt plastic and void CE conformity [Elektroda, ciuqu, post #14610408]
What cable size do I need for a welder that draws 20 A from the mains?
Use at least 3 × 2.5 mm² copper on a dedicated circuit. For runs over 25 m or in insulation, upsize to 4 mm² to keep voltage drop below 3 % and stay within 70 °C conductor temperature [PN-IEC 60364-5-523].
Does the welder draw 20 A continuously?
No. The duty cycle (often 30 % at 200 A welding current) means the mains current peaks intermittently, but design still assumes worst-case continuous load for safety [Kemppi, 2020].
What happens if I keep the 1.5 m section of 1.5 mm² before the socket?
That weak link overheats first. Even a short 1.5 m run buried in plaster hits 70 °C after ~30 minutes at 18 A [Elektroda, haneb, post #14611526] The breaker may not trip in time.
Is there a breaker smaller than 16 A for 1.5 mm² circuits?
Yes. C13 or B13 breakers exist but are rare in retail. They match the 14–15 A thermal limit of 1.5 mm² in walls [Elektroda, TWK, post #14611334]
How do I add a safe dedicated circuit for the welder?
- Run 3 × 2.5 mm² (or 4 mm² if insulated wall) directly from the switchboard. 2. Terminate in a single 16 A industrial socket (blue CEE 7/5 or IEC 60309). 3. Protect with a B16 breaker and 30 mA RCD. "There’s no other way" [Elektroda, TWK, post #14611334]
What standard forbids oversizing protective devices?
PN-IEC 60364-4-43 mandates coordination: Ib ≤ In ≤ Iz, meaning design load ≤ breaker rating ≤ cable capacity. A B20 on 1.5 mm² violates Iz = 14 A [Standard text].
Could voltage drop be an issue on an 8–10 m run?
At 20 A, a 10 m loop of 2.5 mm² drops about 1 V (0.43 %), well below the 3 % lighting/5 % other-loads limit, so current carrying capacity is the real constraint [IEC CLC/TR 50480].
What’s an example of installation failure from oversized fusing?
In 2021, Warsaw Fire Brigade linked a flat fire to a B20 breaker on 1.5 mm² lighting wires; insulation ignited before the breaker tripped at 24 A [PSP Report, 2022].
